As electrical circuits continue to develop in the computer industry, there is an increasing need for the separation of such circuitry so that some circuits reside on a mother board and others reside on daughter cards of various sizes. Daughter cards typically take the form of single in-line memory modules (SIMMs) or dual in-line memory modules (DIMMs). These modules typically contain memory to be utilized as RAM by the microprocessor which may be located on the mother board. The use of daughter cards, however, are not limited to the application of additional memory to be utilized as RAM. Some daughter cards also contain microprocessors of their own to perform various functions such as print acceleration, graphics enhancements or other desired mathematical operations. The movement in the industry towards the use of these daughter cards or modules has precipitated a need for electrical connectors suitable for establishing electrical connections between mother boards and the daughter cards.
Depending upon the architecture and circuit layout of the daughter card, these electrical connectors take various forms. For example, some require electrical connections to only one side of the card edge. Others require redundant electrical connections on both sides of the card edge in order to minimize failures. Finally, some applications require separate and distinct electrical connections along both sides of the board in order to maximize the use of available surface area to achieve a greater number of input/output (I/O) contact points.
An example of a DIMM connector is shown in the cross sectional view of FIG. 1. This connector features an insulative housing 1, a plurality of cavities 2 for receiving a pair of contacts 3. The contacts 3 each have a contact point 6 which is inside a card-receiving slot 7 and a tail section 8 which extends through the bottom surface 4 of the housing 1. These contacts 3 are insertable into the housing from the bottom surface 4. It should be noted that these contacts have a series of bends in order to locate the contact point 6 at a desired position for mating with pads on the edge of an inserted card. It should also be noted that the contact point 6 is located at a distance, D, away from the fulcrum point 5 so that the contacts 3 will pivot away from each other upon card insertion. This causes the contact points 6 to move along an arcuate path as they spread apart from each other. If this motion is analyzed in detail, it is apparent that the arcuate motion contains a vertical force component which is parallel to the card-receiving slot 7 and a horizontal force component which is perpendicular to the card-receiving slot 7. Accordingly, the resultant contact force on the card edge will have vertical and horizontal components. It is desirable to maximize the horizontal force component which is normal to the contact pads in order to establish more reliable electrical connections between the contacts 3 and the pads of the card edge.
One approach to increasing the reliability of these connection is shown in U.S. Pat. No. 5,207,598. This patent teaches a connector for a card edge having a plurality of contact terminals. Each terminal has a generally U-shaped contact portion which extends transverse through a contact cavity slot. The contact portion is horizontally cantilevered from a vertical cantilevered positioning portion. The U-shaped contact portion provides redundant contacts at both sides of the card edge. A problem exists with this design in that it does not utilize both sides of the card edge in order to maximize the number of I/O connections. An additional problem exists in that excess material is required to form the U-shaped portion in order to reach both sides of the card edge.